Method and machine for spirally corrugating tubes



Oct. 13, 1970 'r. R. BUNNELL 7 METHOD AND MACHINE FOR SPIRALLY COBRUGATING TUBES Filed July 23, 1968 2 Sheets-Sheet 1 j? INVENTOR.

'-- I THEODORE RBUNNELL ATTORNEYS Oct. 13, 1970 T. R. BUNNELL METHOD AND MACHINE FOR SPIRALLY CORRUGATING TUBES Filed July 23 1968 2 Sheets-Sheet 2 PUMP FIG. 8

SPIN. SOL.

BRAK

FWD SPIN.

T.D.4-l

SOL.

SOL.-

United States Patent 01 Bee 3,533,267 Patented Oct. 13, 1970 3,533,267 METHOD AND MACHINE FOR SPIRALLY CORRUGATING TUBES Theodore R. Bunnell, Bristol, Conn., assignor, by mesne assignments, to Turhotec, Incorporated, South Windsor, Comm, a corporation of Connecticut Filed July 23, 1968, Ser. No. 746,947 Int. Cl. B21d 15/06 US. Cl. 72-299 35 Claims ABSTRACT OF THE DISCLOSURE A tube of metal or other similarly deformable material is deformed by twisting it against an inserted mandrel to form spiral corrugations therein. The twisting is accomplished by grasping the tube at two axially spaced points and by rotating at one grasped point relative to the other grasped point. During this rotation, one of the grasped points is moved axially relative to the other at an accurately controlled rate in relation to the rate of rotation to control the shape of the corrugations, but this axial movement is not initiated until after a predetermined amount of initial rotation has taken place. Following the twisting operation, the tube may be reversely twisted or axially stretched or both reversely twisted and axially stretched to release it from the mandrel and to improve its shape.

BACKGROUND OF THE INVENTION This invention relates to a method and machine for forming spiral corrugations in tubes of metal or the like, and deals more particularly with such a method and machine wher'ein the corrugations are formed by applying twisting and other forces to the tube and without the use of tools for directly deforming the tube material.

Spirally corrugated tubes, as described herein, are tubes which have two or more corrugations extending spirally or helically along their length with the corrugations appearing much like the threads of a screw. These tubes may be put to many different uses and are of particular value for use in heat exchangers wherein one fluid passing through the tube is put into heat exchange relationship with another fluid on the outside of the tube, the spiral corrugations of the tube serving to increase the surface area of the tube per given unit of length and also serving to cretae a turbulent flow of both the fluid inside of the tube and of the fluid outside of the tube to promote better heat transfer.

The basic concept of making spirally corrugated tubes by twisting the tube against an inserted mandrel is disclosed in prior U.S. patents, No. Re. 24,783, and No. 3,015,355. In using the apparatus and practicing the methods of these prior patents, however, various difiiculties have been encountered including difiiculty in obtaining reliable and repeatedly successful results, difiiculty in producing tubes of uniform dimension and appearance, difficulty in removing the finished tubes from the mandrel after the twisting operation, and difficulty in forming tubes of certain materials. The machine and method of this invention are improvements on the apparatus and methods shown in said prior applications and has as a general object the overcoming of the aforesaid difficulties and the provision of a machine and method capable of producing acceptable tubes at greater rates of production than heretofore possible. I

SUMMARY OF THE INVENTION The present invention resides in a machine and method for spirally corrugating a tube wherein the tube is twisted against a mandrel or other interior restraining means by grasping it at two axially spaced points and rotating it at one grasped point relative to the other grasped point so as to twist and deform it to form spiral corrugations therein. Prior to the twisting operation, the annular wall of the tube is deformed to provide two or more starting indentations, each of which is of an elongated shape and arranged with its major dimension inclined in the same direction as the desired corrugations. These indentations are made simultaneously in order to symmetrically distribute the resulting stresses around the periphery of the tube. During the twisting operation, one of the grasped points is moved axially toward the other at a speed which is accurately controlled in relation to the speed of rotation. This axial movement is initiated at a predetermined time after the initiation of the rotation so as to provide for an initial phase of pure rotation during which the length of tube between the two grasped points is turned or twisted to the point necessary to reach the degree of stress within the tube required for deformation to begin. After the corrugating or twisting operation is completed, one grasped point is rotated in the reverse direction relative to the other and/ or the two points are pulled axially apart to release the tube from the mandrel and/ or to improve the shape of the corrugations.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational View of a machine embodying this invention and for use in spirally corrugating tubes.

FIG. 2 is an enlarged longitudinal sectional view taken through a tube positioned in the machine of FIG. 1.

FIG. 3 is an enlarged transverse sectional view taken on the line of 3-3 of FIG. 1.

FIG. 4 is a perspective view of a tool used for simultaneously forming a number of starting indentations in a tube preparatory to the corrugating operation.

FIG. 5 is a transverse sectional view taken through the tool of FIG. 4.

FIG. 6 is an enlarged fragmentary view taken on the line 6-6 of FIG. 5 and shows the face of one of the forming dies in the tool of FIG. 4.

FIG. 7 is a perspective view showing one end of a tube provided with a number of starting indentations as through the use of the tool of FIG. 4.

FIG. 8 is a schematic diagram showing the hydraulic system of the FIG. 1 machine.

FIG. 9 is a schematic wiring diagram showing the electrical system of the FIG. 1 machine.

DESCRIPTION OF THE PREFERRED EMBODIMENT Turning to the dawings, and first considering FIGS. 1 and 2, FIG. 1 shows a machine embodying the invention and for use in spirally corrugating tubes. The machine includes a bed 2 having a set of ways or other means thereon for slidably supporting a tailstock 3 for axial movement toward and away from an associated headstock 5. The tailstock 3 includes a non-rotative chuck 4 having a set of jaws 6, 6, and the headstock 5 includes a rotative chuck 8 having a similar set of jaws 9, 9. As shown, the jaws 6, 6 of the tailstock chuck 4 and the jaws 9, 9 of the headstock chuck 8 are axially aligned with one another. In use the chucks are axially spaced from one another along the length of the bed 2 and serve to receive a length of tube 10 therebetween and to grasp it exteriorly at two axially spaced points.

As mentioned, the tailstock chuck 4 is fixed against rotation whereas the headstock chuck 8 is rotatable, and for this purpose, the headstock chuck is mounted on a rotatable spindle 12 which is drivingly connected with a gearbox 14 and which receives driving power from an associated electric motor, not shown, connected with the gear box through a clutch in a generally conventional manner. The gearbox includes a means for selectively J controlling the direction of rotation of the chuck 8, and this means and the clutch are operated by an associated electro-mechanical control unit 16 which in response to electrical signals applied thereto moves the clutch be tween engaged and disengaged conditions and the direction selecting means between forward and reverse conditions. Also included in the gear box 14 is a brake for braking the rotational movement of the spindle 12 when the clutch is disengaged. This brake is controlled by another electro-mechanical control unit 18 which, in response to electric signals supplied thereto, applies and releases the brake.

The spindle 12 is preferably hollow so as to allow the tube to be inserted in the chucks 4 and 8 by being inserted through the gear box 14 from the left-hand end thereof, and the chuck 4 is also preferably hollow so as to allow a portion of the tube, if desired, to protrude from the right-hand end thereof.

The machine of FIG. 1 further includes a means for moving the tailstock 3 axially toward the headstock 5. This means may take various different forms and may, for example, consist of an electric motor drivingly connected with the tailstock through a powered jack screw. In the illustrated case, however, the axial movement of the tailstock is provided by an hydraulic system including a double-acting hydraulic cylinder 20, the body of which is fixed to the bed 2 by a suitable bracket 22 and the piston 24 of which is fixed to the tailstock. A pump 26 supplies pressure fiuid to the cylinder through a four-way valve 28. The pump is connected to the valve by a pressure line 30 and a return line 32, and the Valve 28 is connected to the cylinder by a rod end line 34 and a base end line 36. In the rod end line 34 is an adjustable flow rate control valve 38 and in the base end line 36 is a similar adjustable flow rate control valve 40. As explained in more detail hereinafter in connection with FIGS. 8 and 9, the operation of the hydraulic system and of the rotation of the headstock chuck 8 is controlled by an electrical system which includes a control panel 42 and also includes two limit switches 44 and 46 operated respectively by two trip fingers 48 and 50 fixed to the tailstock 3. The switches 44 and 46 are, therefore, operated in response to movement of the tailstock to given positions along the length of the bed 2. They are supported on a bracket 52, fixed to the bed 2, in such a manner as to allow them to be adjustably moved to different positions along the length of the bed.

FIG. 2 is a longitudinal sectional view taken through the tube 10 of FIG. 1 and shows the manner in which the tube-is supported by the jaws 6, 6 of the tailstock chuck and the jaws 9, 9 of the headstock chuck. From this figure, it will be noted that the two sets of jaws exteriorly grasp the tube at two points spaced axially from one another along the length of the tube. A means is also provided for restraining the degree to which the tube may be deformed radially inwardly along various portions of its length, and in the illustrated case this means constitutes a mandrel 54. This mandrel has a first axial portion 56 which is substantially the same diameter as the inside diameter of the tube 10 and which, therefore, along its length restrains the adjacent portion of the tube against any substantial radial inward deformation. Also included in the mandrel is another axial portion 58, separated from the portion 56 by a radial shoulder 60, which is of a uniform diameter substantially less than the inside diameter of the tube. Along its length the mandrel portion 58, therefore, permits the adjacent portion of the tube to deform radially inwardly, but only to the point where the tube engages its outer surface, the tube thereafter being restrained against any further radial inward displacement. The reduced diameter mandrel portion 58 extends from the jaws 6, 6 of the tailstock chuck through and beyond the jaws 9, 9 of the headstock chuck, and at the jaws 9, 9 is slidably supported, if desired, by a bushing 62 which permits the mandrel to slide relative to the headstock chuck as the tailstock is moved toward the headstock. The bushing 62 is not, however, necessary in all instances and may often be eliminated if desired, as the corrugations which are formed in the tube will center the mandrel as the corrugating process takes place. In the illustrated device the large diameter mandrel portion 56 is integral with the small diameter portion 58, but this is not necessary and it could be provided by a bushing loosely received on the small diameter portion 58.

As explained in more detail hereinafter, two or more starting indentations are formed in the wall of the tube 10 prior to the twisting operation. In placing the mandrel 54 in the tube, it is preferably, but not necessarily, so placed that the radial shoulder 60, separating its larger diameter portion 56 from its smaller diameter portion 58, is located directly adjacent the indentations and on the side thereof opposite from the side on which it is desired to form the corrugations, or to the right of the indentations as viewed in FIG. 2. During the twisting operation, the headstock chuck 8 is rotated relative to the tailstock chuck 4 to twist the length of tube 10 positioned between the chucks and as this is done, the tube tends to be deformed along two or more lines, depending on the number of starting indentations, each of which starts at an associated indentation and advances in helical fashion therefrom. The positioning of the mandrel with the radial shoulder 60 adjacent and to the right of the indentations prevents any deformation to the right of the shoulder, as viewed in FIG. 2, and, therefore, assures that the line or lines along which the tube deforms advance in the desired direction, or to the left as viewed in FIG. 2.

It will, of course, be understood that the jaws 6, 6 of the tailstock chuck firmly grip the exterior surface of the portion of the tube 10 positioned therein and press the tube inwardly against the outer surface of the larger diameter mandrel portion 56 so that the large diameter mandrel portion 56 is in effect also grasped by the jaws 6, 6 and held axially in place relative thereto. Likewise, the jaws 9, 9 of the headstock chuck firmly grasp the exterior surface of the portion of the tube inserted therein and press it against the outer surface of the bushing 62 to fix the busing against movement relative to the jaws. The bore of the bushing is, however, of a slightly larger diameter than the diameter of the reduced diameter mandrel portion 58 so that the mandrel may both slide and rotate relative to the bushing. It should also be noted that in FIGS. 1 and 2 the tube 10 positioned in the chucks is shown as it appears at a point part way through the twisting operation. That is, in these figures, the tube has been placed in the chucks and the headstock chuck rotated several times relative to the tailstock chuck, and the tailstock chuck has moved axially forwardly toward the headstock chuck to form a number of corrugations, indicated at 64, 64, in the tube. In this case, the starting indentations were located adjacent the tailstock chuck and as the headstock chuck was rotated the tube deformed along lines which advanced helically from the right to the left, or from the tailstock chuck toward the headstock chuck, to form the corrugations 64, 64. The rotation of the headstock chuck may be stopped at any time, as, for example, the instant of time shown in FIGS. 1 and 2, to deform any desired length of tube, but preferably the chucks are so initially positioned that when the desired length of tube has been corrugated, the lines of deformation will have extended to a point close to the headstock chuck so that substantially all of the tube between the two chucks is corrugated. If this is done, it will be appreciated that the finished length of tube will consist of the two end portions, received in the two chucks, which are uncorrugated, and an intermediate corrugated portion.

If it is desired to have a tube corrugated along its entire length, the two uncorrugated end portions may be cut off. However, it is very often desirable to have the two uncorrugated end portions, which are of uniform circular cross-section, for use, for example, in supporting the tube between its ends by fixing it at each end in a circular opening of a supporting plate. Where this is the case, it is also often desirable that the maximum diameter of the corrugations 64, 64 be no greater than the initial diameter of the undeformed tube so that the tube may be passed through such circular opening. Along the major part of the corrugated portion of the tube, this condition tends to automatically prevail, provided a proper ratio of axial speed to rotative speed is used, however it has been found that the initial corrugations formed immediately adjacent the starting indentations tend to be of a slightly larger diameter than the initial diameter of the tube. Therefore, in accordance with one aspect of this invention, a means is preferably provided to restrain the tube, in the axial zone adjacent the starting indentations, from deforming radially outwardly beyond the initial tube diameter. This means may take various forms but is conveniently provided by the jaws 6, 6 of the tailstock chuck. As shown best in FIG. 3, the jaws 6, 6 are so shaped that in their closed position they surround substantially the entire outer periphery of the tube so that the portion of the tube received therein is restrained against any radial outward displacement. Further, as shown in FIG. 2 and previously mentioned, the tube in being placed in the jaws 6, 6 is so placed that the starting indentations and the radial shoulder of the mandrel 54 are located a substantial distance inboard of the forward ends 66, 66 of the jaws so that the first one or several corrugations formed in the tube during the twisting process are confined by the jaws to the initial diameter of the tube.

After the first one or so corrugations are made, the following corrugations thereafter automatically tend to remain within the initial diameter of the tube and no exterior restraint beyond that provided by the jaws 6, 6 of the tube is required. In addition to providing for restraint against radial deformation, the shaping of the jaws 6, 6, as shown in FIG. 3, so as to surround substantially the full periphery of the tube, also has the effect of uniformly distributing the torque transmitted to the tube over the full periphery thereof and has a beneficial effect on the formation of the corrugations. For the same reason, the jaws 9, 9 of the headstock chuck '8 are also preferably similarly shaped so as to surround substantially the entire periphery of the tube. The chuck jaws or other means need not, however, be used in all instances to restrain the diameter of the starting corrugations, and in some cases it may be desirable to have all corrugations of a substantially larger diameter than the starting tube diameter. This may be readily accomplished by selecting a proper ratio of axial speed to rotative speed.

It should also be noted that although in FIGS. 1 and 2 the tube and mandrel have been shown positioned with the starting indentations located adjacent the stationary chuck, so that in the twisting process the corrugations advance from the stationary chuck toward the rotative chuck, this is not necessary and, if desired, the tube and the mandrel may be positioned in the reverse manner so as to have the starting indentations located adjacent the rotative chuck.

Also, although in the illustrated example the mandrel has been shown with the shoulder 60 positioned adjacent the starting indentations, this procedure is not necessary to the broader aspects of the invention and, if desired, the tube and mandrel may be placed in the chucks so that the starting indentations are located between the chucks and spaced a substantial distance from any mandrel shoulder. In this case, the tube when twisted will usually first deform along helical lines advancing in one axial direction away from the starting indentations until reaching a radial mandrel shoulder restraining further axial advancement of the deformation and will then deform in the other axial direction away from the starting indentations. When this is done the large diameter portion 56 of the mandrel should be a bushing, similar to the bushing 62, loosely received on the small diameter portion of the mandrel so as to allow the mandrel to rotate relative to both of the chucks. Also, in this case, instead of rotating only one chuck both chucks could be rotated so as to cause the tube to deform simultaneously in both axial directions from the starting indentations.

The number of starting indentations made in the Wall of the tube, prior to the twisting thereof, controls the number of helical lines along which the tube deforms. That is, if two indentations are made, the tube, during its twisting, will deform along two helically advancing lines, whereas if three starting indentations are made, the tube will deform during twisting along three simultaneously advancing helical lines. In the past, these indentations have consisted of generally circular depressions usually formed one at a time by driving a round faced tool against the tube wall at each of the locations where an indentation is desired. In accordance with this invention, however, it has been found that these indentations are preferably of an elongated shape and are so orientated that each has its major dimension inclined relative to the longitudinal axis of the tube in the same general direction as the associated helical line along which it is desired to have the tube deform. It has also been found that when more than one indentation is provided, these indentations should be made simultaneously in order to achieve a symmetrical distribution of stresses around the periphery of the tube.

Turning to FIGS. 4 to 7, FIGS. 4 through 6 show an exemplary tool for simultaneously forming four elongated indentations, and FIG. 7 shows a portion of a tube as deformed by the tool of these figures. The tool is indicated generally at 70 in FIG. 4 and consists of a stationary base 72, which may be fixed to a supporting table, including an annular portion 74 for receiving one end of the tube 10. As shown in FIG. 5, the annular portion 74 includes four radial openings each of which slidably receives a die element 76. Each die element includes an elongated working face 78 engageable with the outer surface of the tube 10 and further includes a rounded head 80 at its opposite end. Each element is biased radlially outwardly of the annular portion 74 by a spring 8 2 working between the portion 74 and the head 80. Each of the heads 80 is received in an associated one of four recesses 84, 84 of an annular part 86 which surrounds the stationary annular portion 74 and is movable angularly relative thereto by means of an attached lever or handle. The radially outer boundary of each recess 84 consists of a camming surface which engages the rounded head 89 of the associated die element 76. The shape of each camming surface 90 is such, as seen in FIG. 5, that upon clockwise rotation of the part 86 from its illustrated position, the four die elements 76 are simultaneously driven inwardly to force their working faces 78, 78 into the wall of the tube 10 to thereby simultaneously form the desired elongated starting indentations therein. As shown in FIG. 6, each die element 76 is prevented from rotating about its central axis relative to the part 7-4 by suitable means such as a key 92 received in registered slots in the part 74 and the die element 76. The elongated starting indentations formed in the tube 10 by the device 70 are shown at 94, 94 in FIG. 7.

In accordance with the method of this invention, one of the grasped points of the tube is moved toward the other grasped point during the twisting operation at a rate which is accurately controlled in relation to the speed of rotation. However, this axial movement is delayed at the beginning of the rotation and is not initiated until after a certain amount of rotation has taken place. Since the material of the tube is elastic to a certain degree, this delay in the initiation of the axial movement allows the tube to be turned up or twisted to the point necesary to build up the torque therein to the value required to pro duce stresses at the starting indentations sufiicient to start the desired helical deformation. That is, at the start of the twisting operation, the tube is twisted to the point at which the tube begins to deform at the indentations, or is on the verge of such deformation, before controlled axial movement is initiated. Thereafter, the tube is both twisted and one grasped point moved axially to form the corrugations.

After the tube has been twisted to extend the corrugations to a desired end point, the rotative and axial movements are simultaneously terminated. In some cases this may be the last step in the working of the tube. It will, however, be noted that during the twisting process the wall of the tube collapses inwardly, along the helically advancing lines, against the surface of the reduced diameter mandrel portion 58. Very often, depending on the tube material, if the tube and mandrel are taken from the machine immediately following a twisting operation, the tube will remain pressed against the mandrel with sufficient tightness as to make it difiicult and/ or impossible to remove the mandrel from the tube without severe damage to both. When this is the case, the tube is preferably untwisted to a controlled degree after the twisting operation and before being taken from the machine to loosen the tube from the mandrel. This may be accomplished by merely pulling the tailstock 3 away from the headstock 5 to stretch the tube while allowing the headstock chuck 8 to free wheel. That is, as the tube is stretched, a certain amount of untwisting will take place as a result of the tension forces produced and without the need for reversely driving the headstock chuck 8, if the chuck is allowed to rotate freely. However, if desired, the headstock chuck may be driven in the reverse direction as the tailstock chuck is moved away therefrom to obtain a more precise control over the finished shape of the tube. Also, in some cases, the untwisting might be accomplished by driving the headstock chuck in the reverse direction while allowing the tailstock to move freely away from the headstock. In addition to loosening the tube from the mandrel, this untwisting of the tube after the twisting operation tends to correct for possible irregularities in the spacing between the corrugations and to otherwise make more uniform and improve the appearance of the finished tube. Some tube materials have a sufiicient degree of elasticity that after the twisting operation the tube tends to untwist a sufficient amount by itself to loosen it from the mandrel, but even in this case some untwisting may be desirable to improve the character of the finished tube.

Where the untwisting operation is performed by both moving the tailstock under power away from the headstock and by reversely driving the headstock chuck, the speed of axial movement and the speed of rotative movement are both preferably accurately controlled to maintain a precise ratio between such speeds and also, dependent upon the metallurgy and dimensions of the tube materials being formed, as in the twisting operation, the relative relationship between the rotational and axial movements must be precisely and selectively controlled and synchronized. Depending upon the tube material and/or its configuration, the axial movement during untwisting may precede, be simultaneous with, or lag the initiation of the reverse rotative movement so that a controlled amount of reverse torque is maintained in the tube as the axial movement occurs.

In the machine of FIG. 1, the axial movement of one grasped point toward the other grasped point is achieved and controlled by the hydraulic cylinder and its associated hydraulic circuit. Considering both FIG. 1 and FIG. 8, the fourway valve 28 is of conventional construction and is operable to control the direction of movement of the piston rod 24 and tailstock 3. The valve includes a spindle, represented at 96 in FIG. 8, and two solenoids 98 and 100, referred to respectively as the forward solenoid and the reverse solenoid, which, when energized, position the spindle so as to obtain either forward or reverse movement of the piston rod 24. That is, when the forward solenoid 98 is energized, the spindle 96 is moved to the left in FIG. 8 so that pressure fluid is supplied to the base end of the cylinder 20 and is vented from the rod end of the cylinder, thereby producing forward or extending movement of the piston rod 24. Similarly, when the reverse solenoid 100 is energized, the spindle 96 is shifted to the right in FIG. 8 to supply pressure fluid to the rod end of the cylinder and to vent it from the base end, thereby obtaining reverse or retracting movement of the piston rod.

The rate at which the piston rod is moved in the forward direction is controlled by the adjustable flow-rate control valve 38 in the rod end line 34. This valve is of a standard construction and includes an adjustable restriction 102 and a check valve 104. The adjustable restriction 102, during the forward movement of the piston rod 24, controls the rate at which fluid is vented from the cylinder 20 and thereby controls the rate of movement of the piston rod. The rate of flow permitted by the valve 38 is controlled by a manually adjustable knob shown at 105 in FIG. 1. The check valve 104 prevents hydraulic fluid from bypassing the restriction 102 during the forward movement of the piston rod 24, but does allow such bypassing during reverse movement of the piston rod. Similarly, the speed of the piston rod 24 during reverse movement is controlled by the adjustable flow rate control valve 40 which, similar to the unit 38, includes an adjustable restriction 106 and a check valve 108. The restriction 106 controls the rate of flow of hydraulic fluid through the line 36 during the reverse movement of the piston rod, to control the rate of speed of the rod. The rate of flow permitted by this restriction is adjustable by the knob shown in FIG. 1. The check valve 108 prevents hydraulic fluid from bypassing the restriction 106 during reverse movement of the piston rod, but does allow such bypassing during forward motion of the piston rod.

Accordingly, in the hydraulic system shown in FIGS. 1 and 8, the speed of the piston rod 24 may be accurately controlled both in its forward and reverse movement by adjusting the knobs 105 and 110 of the flow rate control valves 38 and 40. In some cases, it may not be necessary to have accurate control over the speed of the reverse axial movement and in such instances, the flow rate control valve 40 may be eliminated if desired.

Also, in the machine of FIG. 1, the control for the rotative movement of the head stock chuck 8 is so interconnected with the control for the axial movement of the tailstock chuck and other controls that the machine, once started, will automatically perform in sequence a complete corrugating operation which includes: (1) initiation of forward rotative motion of the headstock chuck, (2) initiation of forward axial movement of the tailstock a predetermined time after the initiation of the forward rotative movement, (3) simultaneous stopping of both the forward rotative and the forward axial movement after a desired amount of twisting has taken place, (4) initiation of reverse rotation of the headstock chuck, (5) initiation of reverse movement of the tailstock a predetermined time after the initiation of the reverse rotation of the headstock, and (6) simultaneous stopping of both the reverse rotative and the reverse axial movement after a desired amount of untwisting has taken place. The means for providing this automatic operation is the electrical system of FIG. 9 which is controllable from the control panel 42 of FIG. 1. It should, of course, be understood that the illustrated control system is exemplary only and that other systems, depending on the requirements, may be used wherein the reverse rotative and reverse axial movements are started simultaneously or wherein the reverse axial movement is started first and the reverse rotative movement initiated a predetermined time after the initiation of the reverse axial movement.

Referring to FIG. 9, the electrical system there shown consists of a number of relays, solenoids, time delays and other standard electrical components connected between two power lines 112 and 114. The wiring of the system and its detailed construction may be best understood by considering its operation through one complete corrugating cycle. At the start of such a cycle, a fresh tube is positioned between the headstock chuck and the tailstock chuck of the machine and the condition of the electrical system is that as shown in FIG. 9. To start the cycle, the start pushbutton 116 is depressed. This energizes the coil 118 of relay A and closes the associated relay contacts A1 to maintain a latching circuit through the relay coil 118 passing through the normally closed contacts of the limit switch 44. The energization of relay A also closes contacts A-2 and energizes the forward spindle solenoid 120. The forward spindle solenoid 120 is a part of the electro-mechanical control unit 16 of FIG. 1 and, when energized, conditions the clutch and gearbox in such a manner as to cause the headstock chuck to be driven in the forward rotative direction. At the same time as the forward spindle solenoid 120 is energized the coil 122 of a first time delay relay is also energized. A predetermined time after the energization of the time delay coil 122, the associated contacts are operated. These contacts include contacts TD1-1 which are closed after the running of the time delay and which when closed energize, through the now closed contacts A-3, the forward solenoid 98 of the fourway hydraulic valve 28 to cause the cylinder 20 to be operated in the forward manner to extend the piston rod 24 and move the tailstock toward the headstock. The time delay contacts TD1-1 are connected in parallel with a pushbutton 124 which may be operated manually at any time, as when placing a new tube in the machine, to achieve forward movement of the tailstock.

The forward movement of the tailstock toward the headstock continues until the trip finger 48 engages and operates the limit switch 44. This operation of the limit switch 44 de-energizes the coil 118 of the relay A and by the closing of its normally open contacts energizes the coil 126 of a second time delay relay and the coil 127 of relay B, this energization taking place through the normally closed contacts TD2-1 of the second time delay relay.

The de-energization of the coil 118 of relay A opens the contacts A-2 and de-energizes the forward spindle solenoid 120 to disengage the clutch associated with the headstock chuck and to thereby remove the driving power therefrom. The closing of the contacts B-1, resulting from energization of the coil 127 of the relay -B, energizes the brake spindle solenoid 128, a part of the electromechanical unit 18 of FIG. 1, which energizes the brake for the headstock chuck so as to immediately bring it to a stop. The opening of the contacts A-3, upon deenergization of the relay A, also de-energizes the forward solenoid 98 to stop the forward movement of the tailstock. Therefore, termination of the forward rotative movement of the headstock by disengaging its clutch and applying its brake and termination of the forward movement of the tailstock 'by operating the four-way valve 28 are substantially simultaneously accomplished.

After the running of the delay period provided by the second time delay, its contacts are operated. This includes opening of the contacts TD2-1 which de-energizes the coil 127 of relay B, thereby opening the contacts B1 and de-energizing the spindle brake solenoid 128 to release the spindle. It also includes a momentary closing and then reopening of the contacts TD2-2. During the moment that the contacts TD22 are closed, the coil 130 of the relay C is energized and a latching circuit for maintaining the relay coil 130 energized after the reopening of the time delay contacts TD2-2 is obtained by the closing of the contacts C-l associated with the relay C.

The energization of relay C also closes contacts C-2 which energizes the coil 132 of a third time delay relay and the reverse spindle solenoid 134. The reverse spindle solenoid 134 is part of the electro-mechanical unit 16 of FIG. 1 and when energized causes the clutch and gearbox associated with the headstock 5 to be conditioned in such a manner as to cause the headstock chuck to be rotatively driven in the reverse or untwisting direction. A predetermined time after the coil 132 of the third time delay relay is energized, the associated contacts TD3-1 are closed to energize through the now closed contacts C-3 the reverse solenoid of the four-way valve to cause the cylinder 20 to retract the piston rod 24 and move the tailstock in the reverse direction or to the right in FIG. 1.

This reverse movement of the tailstock, and concurrent reverse rotation of the headstock, continues until the trip finger 50 engages the limit switch 46 and thereby, by opening its normally closed contacts, de-energizes the coil of the relay C. This de-energization of the relay C reopens the contacts C-2 to de-energize the reverse spindle solenoid 134 and opens the contacts C 3 to de-energize the reverse solenoid 100. The operation of the limit switch 46 also closes its normally open contacts and in so doing energizes the coil 137 of a fourth time delay relay. Included in this time delay relay is a set of normally open contacts TD4-1 which are closed immediately upon energization of the coil 137 and which are thereafter opened after the running of a predetermined delay period. During this period, the contacts TD4-1 complete a circuit to energize the spindle brake solenoid 128 which in turn applies the spindle brake to quickly stop the spindle rotation. Therefore, as soon as the limit switch 46 is operated during the reverse axial movement of the tailstock the reverse rotative movement and the reverse axial movement are both simultaneously terminated. This completes the corrugating operation and thereafter the tube may be removed from the chucks and the tailstock returned to its starting position for receiving a fresh tube. A pushbutton 136 is connected in parallel with the contacts C-3 and TD3-1 so as to permit the reverse solenoid 100 to be energized manually at any time to obtain reverse movement of the tailstock.

From the foregoing description of the operation of the circuit of FIG. 9, it will be noted that the first time delay relay controls the amount of time which elapses between the initiation of the forward rotative movement and the forward axial movement. This delay period as provided by this unit is in turn adjustable by the knob 138 of FIG. 1. Likewise, the second time delay relay controls the braking period or the time between the stop of the twisting operation and the start of the nntwisting operation and this relay is adjustable by the knob 140 of FIG. 1 to vary the length of this delay period. The third time delay relay controls the delay between the start of the reverse rotative movement of the headstock and the start of the reverse axial movement of the tailstock and it includes a knob 142 for adjusting this delay period.

The rotative drive for the headstock chuck 8, provided by the gearbox 14 and its associated motor, is such that the headstock chuck is driven at a uniform angular speed which in the forward direction may be represented by o The axial movement of the tailstock chuck during forward movement thereof is also accurately controlled and maintained at a uniform rate by the adjustable flow rate control valve 38, and this axial or linear velocity may be represented as V Since the angular movement w; and the axial movement V are uniform, their ratio w V is a constant. This ratio is directly related to the pitch angle or lead of the corrugations formed during the twisting operation and, therefore, by varying this ratio, the pitch angle or lead of the resulting corrugations may be readily varied to produce the desired pitch angle or lead. In the illustrated machine, the means for varying this ratio is the adjustable flow rate control valve 38 which may be used to adjust the axial speed V The headstock chuck 8 is also driven by the gearbox at a uniform reverse speed during reverse rotation, which speed may be represented as w," The adjustable flow rate control valve 40 maintains the reverse axial movement of the tailstock at a uniform speed V and, therefore through the use of the adjustable flow rate control valve 40, the ratio 01 V of the reverse speeds may also be maintained at any desired fixed value during the untwisting operation.

Although the drawings and description relate to one embodiment of this invention, it should be understood that there is no intention to limit the invention to the disclosed construction and processes and instead it is intended that the invention should extend to all alternative embodiments, constructions and processes falling within the scope of the following claims.

What is claimed is:

1. A machine for spirally corrugating tubes, said machine comprising two aligned chucks for grasping a length of tube at two respective points spaced from one another along the axis of said tube, a mandrel for insertion in a length of tube grasped by said chucks and having one axial portion of substantially smaller diameter than the initial inside diameter of said tube, rotative drive means for rotating one of said chucks in a forward direction relative to the other of said chucks so as to twist the length of tube grasped thereby to form spiral corrugations therein the minimum inside diameter of which is controlled by said mandrel, axial drive means for driving one of said chucks axially in a forward direction toward the other of said chucks, means for initiating the energization of said rotative drive means to cause it to rotate the associated one of said chucks in a forward direction relative to the other of said chucks, and means responsive to said latter initiation of the energization of said rotative drive means for thereafter automatically initiating the energization of said axial drive means to cause it to drive the associated one of said chucks in a forward direction toward the other of said chucks after the running of a predetermined delay period following said initiation of the energization of said rotative drive means.

2. A machine for spirally corrugating tubes as defined in claim 1 further characterized by each of said chucks including a set of jaws which when in grasping relation with a length of tube surround substantially the entire circumference of said tube.

3. A machine for spirally corrugating tubes as defined in claim 1 further characterized by said means for initiating the energization of said rotative drive means ineluding an electrical switch, and said means for thereafter automatically initiating the energization of said axial drive means including a time delay relay connected with said switch so as to be energized by the operation thereof and having a pair of contacts which are operated following the running of said predetermined delay period, said contacts being connected with said axial drive means and operable to control the energization thereof.

4. A machine for spirally corrugating tubes as defined in claim -1 further characterized by means for selectively varying the ratio w /V where o is the angular velocity at which one chuck is rotated in the forward direction relative to the other chuck by said rotative drive means and V is the linear velocity at which one chuck is moved in the forward axial direction relative to the other chuck.

5. A machine for spirally corrugating tubes as defined in claim 4 further characterized by said means for varying the ratio w /V including a means for selectively varying the speed at which said axial drive means moves one chuck forwardly toward the other chuck.

6. A machine for spirally corrugating tubes as defined in claim 5 further characterized by said axial drive means for driving one of said chucks forwardly toward the other of said chucks comprising an hydraulic motor, and said means for selectively varying the ratio w V including an adjustable flow rate control valve for controlling the rate of flow of hydraulic fluid to said hydraulic motor as sand hydraulic motor is operated to move said one chuck toward said other chuck.

7. A machine for spirally corrugating tubes as defined in claim 1 further characterized by said axial drive means for driving one of said chucks axially forwardly toward the other of said chucks also being operable in a reverse manner to drive such one chuck in the reverse direction axially away from the other chuck, said rotative drive means for rotating one of said chucks forwardly relative to the other of said chucks also being operable in a reverse manner so as to tend to untwist corrugations existing in a length of tube grasped between said chucks and formed by a prior twisting operation, means for automatically de-energizing said rotative drive means and said axial drive means in response to movement of one chuck to a given axial position relative to the other chuck during a twisting operation, means for thereafter automatically initiating the energization of said rotative drive means and said axial drive means to cause said rotative drive means to rotate its associated chuck in the reverse direction and to cause said axial drive means to move its associated chuck away from the other of said chucks according to a predetermined program.

8. A machine for spirally corrugating tubes defined in claim 7 further characterized by means for automatically tie-energizing said rotative drive means and said axial drive means in response to movement of one chuck to a given axial position relative to the other chuck during an untwisting operation.

9. A machine for spirally corrugating tubes as defined in claim 7 further characterized by a brake for braking the rotation of the chuck driven by said rotative drive means, and means for energizing said brake to brake the rotation of said latter chuck in response to de-energization of said rotative drive means.

10. A machine for spirally corrugating tubes, said machine comprising two aligned chucks for grasping a length of tube at two respective points spaced from one another along the axis of said tube, a mandrel for insertion in a length of tube grasped by said chucks and having one axial portion of substantially smaller diameter than the initial inside diameter of said tube, rotative drive means for rotating one of said chucks in a forward direction relative to the other of said chucks so as to twist the length of tube grasped thereby to form spiral corrugations therein the minimum inside diameter of which is controlled by said mandrel, axial drive means for driving one of said chucks axially in a forward direction toward the other of said chucks, and means for selectively varying the ratio w /V where o is the angular velocity at which one chuck is rotated in the forward direction relative to the other chuck by said rotative drive means and V; is the linear velocity at which one chuck is moved in the forward axial direction relative to the other chuck by said axial drive means.

11. A machine for spirally corrugating tubes as defined in claim 10 further characterized by said means for varying the ratio w /V including a means for selectively varying the speed at which said axial drive means moves one chuck toward the other of said chucks.

12. A machine for spirally corrugating tubes as defined in claim 10 further characterized by said rotative drive means for rotating one of said chucks forwardly relative to the other of said chucks also being operable in a reverse manner so as to tend to untwist corrugations existing in a length of tube grasped between said chucks and formed by a prior twisting operation, said axial drive means for driving one of said chucks axially forwardly toward the other of said chucks also being operable in a reverse manner to drive such one chuck axially away from the other chuck, and means for selectively varying the ratio of to /V independently of the ratio of w;/ V where w, is the angular velocity at which one chuck is rotated in the reverse direction relative to the other chuck by said rotative drive means and V is the linear velocity at which one chuck is moved in the reverse axial direction relative to the other chuck.

13. A machine for spirally corrugating tubes, said machine comprising two aligned chucks for grasping a length of tube at two respective points spaced from one another along the axis of said tube, a mandrel for insertion in a length of tube grasped by said chucks and having one axial portion of substantially smaller diameter than the initial inside diameter of said tube, rotative drive means for rotating one of said chucks in a forward direction relative to the other of said chucks so as to twist the length of tube grasped thereby to form spiral corrugations therein the inside diameter of which is controlled by said mandrel, axial drive means for driving one of said chucks axially in a forward direction toward the other of said chucks during said rotation, and means for selectively varying the rate at which said axial drive means moves said one chuck axially in said forward direction.

14. A machine for spirally corrugating tubes as defined in claim 13 further characterized by said axial drive means including an hydraulic cylinder and two hydraulic lines for respectively supplying hydraulic fluid to and venting it from said hydraulic cylinder, and said means for selectively varying the rate at which said axial drive means moves said associated chuck axially in a forward direction comprising an adjustable flow rate control valve in one of said hydraulic lines.

15. The method for spirally corrugating a tube which method comprises the steps of: providing a tube having an annular Wall of substantially circular cross-section, forming at least one indentation of an elongated shape in said wall of said tube with the major dimension thereof inclined relative to the axis of said tube, positioning a mandrel having at least one axially extending portion of lesser diameter than the inside diameter of said tube within said tube so that said lesser diameter portion is located at the axial zone of said indentation and extends therefrom in one direction axially of said tube, grasping said tube at first and second axial zones axially spaced from one another and located on opposite sides of said indentation, and thereafter rotating said tube at one of said axial zones relative to the other of said axial zones about its longitudinal axis and in such a direction that the helix defined in part by said inclined elongated indentation tends to be wound in a tightening direction and to thereby deform said tube along a line which advances helically away from said elongated indentation as said rotation contiuues.

16. A method for spirally corrugating a tube as defined in claim 15 further characterized by restraining said tube against radial inward deformation along an axial zone located directly adjacent one side of said indentation so that when said tube is rotated it is confined to deforming along a line which advances helically away from the opposite side of said elongated indentation.

17. The method for spirally corrugating a tube as tube as defined in claim 16 further characterized by said step of restraining said tube against radial inward deformation comprising the step of providing said mandrel with another axially extending portion of a diameter substantially equal to the inside diameter of said tube and separated from said one axially extending portion of lesser diameter by a radial shoulder, and positioning said mandrel in said tube with said shoulder located adjacent said one side of said indentation.

18. The method of spirally corrugating a tube as defined in claim 16 further characterized by restraining said tube against radial outward displacement of its annular wall in an axial zone located adjacent said one indentation and extending for some distance beyond said indentation in a direction away from said opposite side thereof.

19. The method of spirally corrugating a tube as defined in claim 15 further characterized by said step of forming at least one elongated indentation in said annular wall of said tube being accomplished by simultaneously forming a plurality of such indentations in said wall with each of said indentations having its major dimension inclined in the same direction relative to the longitudinal axis of the tube and with all of said indentations being located in a common axial zone of said tube.

20. The method of spirally corrugating tube as defined in claim 15 further characterized by axially moving one of said first and second axially spaced zones toward the other during said rotation at a speed controlled in relation to the speed of rotation.

21. The method of spirally corrugating a tube as defined in claim 20 further characterized by delaying the initiation of said step of axially moving one of said first and second zones toward the other until a predetermined initial amount of rotation has taken place.

22. The method of spirally corrugating a tube as defined in claim 15 further characterized by continuing said rotation until a desired length of tube between said first and second axial zones has been corrugated, stopping said rotation, and thereafter rotating said tube at one of said axial zones relative to the other of said axial zones in the opposite direction so as to tend to untwist the corrugations formed by the preceding rotation.

' 23. The method of sprally corrugating a tube as defined in claim 22 further characterized by driving one of said first and second axially spaced zones away from the other during said reverse rotation at a speed controlled in relation to the speed of rotation.

24. The method of spirally corrugating a tube as defined in claim 23 further characterized by controlling the initiation of said step of axially driving one of said first and second axially spaced zones away from the other and the initiation of said step of reversely rotating one of said axial zones in accordance with a predetermined program.

25. The method of spirally corrugating a tube as defined in claim 15 further characterized by continuing said rotation until the desired length of tube between said first and second axial zones has been corrugated, stopping said rotation, and thereafter pulling one of said first and second axially spaced zones away from the other while allowing said tube at one of said zones to rotate freely relative to the other of said zones.

26. The method of spirally corrugating a tube which method comprises the steps of: providing a tube having an annular wall of substantially circular cross-section, forming at least one indentation in said Wall of said tube, positioning a mandrel having at least one axially extending portion of lesser diameter than the inside diameter of said tube within said tube so that said lesser diameter portion is located at the axial zone of said indentation and extends therefrom in one direction axially of said tube, grasping said tube at first and second axially spaced zones located on opposite sides of said indentation restraining said tube against radial inward deformation along an axial zone located directly adjacent one side of said indentation so that when said tube is rotated it is confined to deforming along a line which advances helically away from the opposite side of said elongated indentation, restraining said tube against radial outward displacement of its annular wall in an axial zone located adjacent said indentation and extending for some distance beyond said indentation in the direction away from the opposite side thereof, and thereafter rotating said tube at one of said axial zones relative to the other of said axial zones about its longitudinal axis to deform said tube along a line which advances helically away from said indentation as said rotation continues.

27. The method of spirally corrugating a tube which method comprises the steps of providing a tube having an annular wall of substantially circular cross-section, forming at least one indentation in said wall of said tube,

grasping said tube at first and second axial zones axially spaced from one another along the length of said tube and located on opposite sides of said indentation, restraining said tube against radial inward deformation along an axial zone beginning at one point near said indentation and extending for some axial distance in one direction therefrom, restraining said tube against radial inward deformation beyond a given cylindrical surface of lesser diameter than the inside diameter of said tube along an axial zone beginning at said one point and extending in the other direction therefrom, restraining said tube against radial outward deformation in an axial zone beginning near said one point and extending for some distance beyond said indentation in said other direction, and thereafter rotating said tube at one of said axial zones relative to the other of said axial zones so as to deform it along a line which advances helically away from said indentation as said rotation continues.

28. The method for spirally corrugating a tube as defined in claim 27 further characterized by said steps of restraining said tube against radial inward deformation being accomplished by providing a mandrel having a first axial portion of substantially the same diameter as the inside diameter of said tube and a second axial portion of lesser diameter than said inside diameter of said tube and separated from. said first portion by a radial shoulder, and positioning said mandrel in said tube prior to said rotation with said radial shoulder located adjacent said indentation.

29. A method for spirally corrugating a tube as de fined in claim 28 further characterized by said step of restraining said tube against radial outward displacement being accomplished by grasping said tube at said indentation by means of a chuck having jaws which surround substantially the entire circumference of said tube and extend axially for some distance in both directions from said indentation.

30. The method of spirally corrugating a tube, which method comprises the steps of: providing a tube having an annular wall of substantially circular cross-section, forming at least one indentation in said wall of said tube, grasping said tube at first and second axial zones axially spaced from one another along the length of said tube and located on opposite sides of said indentation, restraining said tube against radial inward deformation beyond a given cylindrical surface of lesser diameter than the inside diameter of said tube along an axial zone beginning at said indentation and extending therefrom in one direction axially of said tube, rotating said tube at one of said axial zones relative to the other of said axial zones so as to deform it along a line which advances helically away from said indentation in said one axial direction as said rotation continues, and axially moving one of said first and second axially spaced zones toward the other during said rotation at a speed controlled in relation to the speed of rotation.

31. The method of spirally corrugating a tube as defined in claim 30 further characterized by delaying the initiation of said step of axially moving one of said first and second axially spaced zones toward the other until a predetermined initial amount of rotation has taken place.

32. The method of spirally corrugating a tube, which method comprises the steps of: providing a tube having an annular wall of substantially circular cross-section,

forming at least one indentation in said wall of said tube, grasping said tube at first and second axial zones axially spaced from one another along the length of said tube and located on opposite sides of said indentation, restraining said tube against radial inward deformation beyond a given cylindrical surface of lesser diameter than the inside diameter of said tube along an axial zone beginning at said indentation and extending therefrom in one direction axially of said tube, rotating said tube at one of said axial zones relative to the other of said axial zones so as to deform it along a line which advances helically away from said indentation in said one axial direction as said rotation continues, continuing said rotation until a desired length of tube between said first and second axial zones has been corrugated, stopping said rotation and thereafter rotating said tube at one of said axial zones relative to the other of said axial zones in the reverse direction so as to tend to untwist the corrugations formed by the preceding rotation.

33. The method of spirally corrugating a tube as defined in claim 32 further characterized by moving one of said first and second axial zones away from the other during said reverse rotation at a speed controlled in relation to the speed of rotation.

34. The method of spirally corrugating a tube as defined in claim 33 further characterized by delaying one of said steps of axially moving one of said first and second axially spaced zones away from the other and reversely rotating said tube at one of said axial zones until a predetermined time after the initiation of the other of said steps.

35. The method of spirally corrugating a tube, which method comprises the steps of: providing a tube having an annular wall of substantially circular cross-section, forming at least one indentation in said wall of said tube, grasping said tube at first and second axial zones axially spaced from one another along the length of said tube and located on opposite sides of said indentation, restraining said tube against radial inward deformation beyond a given cylindrical surface of lesser diameter than the inside diameter of said tube along an axial zone beginning at said indentation and extending therefrom in one direction axially of said tube, rotating said tube at one of said axial zones relative to the other of said axial zones so as to deform it along a line which advances helically away from said indentation in said one axial direction as said rotation continues, continuing said rotation until a desired length of tube between said first and second axial zones has been corrugated, stopping said rotation, and thereafter pulling one of said first and second axially spaced zones away from the other while allowing said tube at one of said zones to rotate freely relative to the other of said zones.

References Cited UNITED STATES PATENTS Re. 24,783 2/ 1960 Humphrey 72-299 3,015,355 1/1962 Humphrey 72--299 3,117,471 1/1964 OConnell et al. 72299 LOWELL A. LARSON, Primary Examiner US. Cl. X.R. 72371 

